Driving mechanism for tremolos



May 5, 1953 c. P. KRUEGER DRIVING MECHANISM FOR TREMOLOS FIG.

Filed April 14, 1948 as 65 48 so 92 56 59 e7 FIG.3

77 INVENTOR CONRAD P. KRUEGER mg ATTO NEYS Patented May 5, 1953 DRIVING MECHANISM FOR TREMOLOS Conrad P. Krueger, Hopkins, Minn., assignor to Patent Management, Incorporated, Minneapolis, Minn., a corporation of Minnesota Application April 14, 1948, Serial N 0. 20,932

2 Claims. (01. 74- 111) My invention relates to tremolos for musical instruments and particularly to musical mar-11 ments having sound generators each driven by a mechanically rotating element such as a shaft or the like operating at a substantially uniform rate of speed.

An object of the invention resides in providing a tremolo capable of producing variations in tone frequency as distinguished from variations in tone intensity.

An object of the invention resides in providing a tremolo embodying a driven element driven by the driving element and a flexible driving connection between said driving and driven elements.

Another object of theinvention resides in providing a tremolo in which the driven element is periodically retarded to produce the tremolo effect and during which time the relative movement between the driving element and driven element is effected through the flexible driving connection.

A still further object of the invention resides in providing a mechanical brake mechanism for periodically retarding the driven element.

An object of the invention resides in providing spring means acting between the driving element and driven element in a tangential direction and accommodating relative rotational movement therebetween.

A still further object of the invention resides in constructing the driving element and driven element with juxtaposed concentrically revoluble plates, and in providing circumferentially spaced spring anchors on one plate with intervening openings therein and in further providing spring anchors on the other plate extending through said openings, together with springs, each anchoredat one end to one of said first named spring anchors and at its other end to one of the other spring anchors.

In the drawings:

Fig. 1 is a side elevational view of a portion of a musical instrument illustrating an embodi ment of my invention applied thereto and showing parts of the invention in section.

Fig. 2 is a cross sectional view taken on line 2-2 of Fig. 1.

Fig. 3 is a view similar to Fig. 2 illustrating a portion of the structure disclosed therein. and showingsome of the parts in altered position. v

Fig. 4 is a fragmentary sectional view taken on line i4 of Fig. 3.

For the purpose of illustrating my invention I have shown in the drawings a portion of a- 2 g musical instrument In. Since the invention does not concern itself with the construction of the musical instrument itself, only so much of the instrument as concerns itself with the tremolo has been shown. This instrument comprises a frame II which carries a number of tone generators one of which is indicated at l2. The tone generators are operated by means of a driven shaft [3 which is driven by a driving shaft [4 connected to an electric motor l5. These parts will now be described in detail.

The frame 10 comprises a number of elongated rods i6 on which are mounted a plurality of frame members Ila, lib, etc., there being one such frame member for each tone generator. The frame 10 in addition, includes another frame member 18 which constitutes an end frame member for said frame and which is also mounted on the rods l6. Sleeves l9 encircle the rods 16 and are disposed between the frame members lla, llb etc., and I8 and nuts 2| screwed upon the ends of the said rods clamp the parts securely together. Issuing outwardly from the frame [9 is a shelf 22 which is attached to the frame member Ha and to the end frame member 28 by means of angles 23 and 24 riveted to each frame member and said shelf. This shelf is braced relative to the frame ill by means of a brace 25 which is secured to said shelf and the frame member Ila by bolts 25.

The motor [5 may be of conventional construction and is preferably of the synchronous type. This motor is secured to the shelf 22 by means of bolts 2! which pass through feet 28 on said motor and are threaded into the shelf 22. The driving shaft I4 is the rotor shaft of the motor l 5 and is rotatably mounted in the usual bearings of the motor. This shaft extends through the end frame member l8 and is operatively connected to the driven shaft [3 as will be subsequently described.

The driven shaft I3 extends through all of the frame members Ila, lib etc., and is rotatably mounted in a number of bearings, one of which is indicated at 29 and which are attached to certain of the frame members Ila, l'lb, etc. The shaft l3 in the form of the invention illustrated, is disposed in axial alignment with the shaft 14 and the end of the same extends up to and in close proximity to the end of the shaft 14.

The tone generator 12 consists of a magnet 3| having a core 32 and a winding 33 mounted on said core. The core 32 is attached to the framev member lib by means of a screw 34 which is threaded into the core 32. The other end 35 of the core 32 forms a pole which cooperates with U a tone wheel 35. The tone wheel may be a serrated ring of ferrous metal or any other construction having a number of spaced teeth or sections adapted to cooperate with the pole 35 upon rotation of said wheel to vary the reluctance of the magnetic circuit containing the core 32 and to correspondingly vary the current flowing through the winding 33. The tone wheel 35 is mounted upon a shaft 31 which is rotatably supported in a bearing 33. Bearing 322 is attached to bracket 39 which is secured to the frame member Ila by means of an angle 41 similar to the angles 23 and 2d. The lower end of the shaft 31 has secured to it a driven wheel 62 which has mounted on it a rubber tire 43. This contacts a disc 5 attached to a hub 45. The hub is mounted on shaft i3 and is held in position by means of a set screw 56. The wheel 42 can be adjusted on the shaft 37 to vary the speed ratio between said wheel and the disc 44 whereby the tone wheel 35 may be driven at any suitable speed within certain limits and tones of the desired frequencies can be produced by the various generators. The windings 33 of the various tone generators are connected through suitable switches operated by the keys of a keyboard of the musical instrument to suitable electrical circuits including an amplifier and a loud speaker whereby the electrical impulses set up in the magnetic circuit including the core 32, are converted into audible sounds.

The invention proper includes a plate 43 which has issuing from it a hub 49. I-Iub 49 is secured to the shaft :3 by means of a set screw 5|. The

plate 48 is disposed at the end of the shaft l3 and lies between the two frame members Na and it. The outermost portion of the plate 48 has a flange 52 extending therefrom and which forms a brake drum. Within the drum 52 is disposed a plate 53 similar to the plate 48 and plate 48 and between the openings 55 are provided studs 53 which are similar to the studs Eland. which are arranged at the same distance from the axis at the shaft 13a and M as the studs 57. Between the studs 51 and 58 are located tension coil springs 59 which have their ends Bl hooked over'said studs. These springs are normally slightly tensioned and serve to connect the two shafts M and [3 together. By means of this construction a driving connection between the two shafts is afforded including driving element 53 and a driven element 42 permitting of relative rotation or movement between the elements.

Cooperating with the brake drum 52 is a brake shoe 35 which is mounted on and attached to a lever 52. Lever is angular in form having a vertical leg 9i and a horizontal leg 92. Lever 62 is pivoted to the end frame I! by means of a stud 53 which extends outwardly therefrom and which passes through the leg 9|. A nut 54 screwed on the end of said stud holds the same attached to said frame member. The lever 52 is urged downwardly as viewed in Figs. 2 and 3 by means of a compression coil spring 55 which engages the leg 92 and is attached to a screw d 66. This screw is threaded in a bracket Bl attached to the frame member 18. A look nut 68 on said screw holds the same in position. The leg 92 of the lever 62 at the forward end thereof is formed with a hole 59 through which a Bowden wire ll extends. This wire has a collar 12 secured to the end of it and which is adapted to engage the under surface of the leg 32 and to raise said lever in opposition to the spring 65 to disengage the shoe to from the brake drum 52.

For operating the tremolo, a friction wheel 16 is employed which is mounted on a stub shaft 15 which extends outwardly from the end frame member [8. The friction wheel 16 is provided with a hub 93 through which the shaft 74 extends and a washer 94 on the end of said shaft holds the wheel in place. On the wheel 15 is a tire Tl which is adapted to engage a friction roller i9 secured to the shaft ill. By means of this construction the wheel 15 is driven from the shaft It at a suitable speed. Mounted on the wheel 13 is a cam '13 in the form of an annulus which is eccentrically disposed relative to the shaft i4. Screws 95 pass through the cam 13, and through spacers 9t and are threaded into the wheel is to hold the cam 73 mounted thereon to rotate with it. Cooperating with the cam 13 is a cam follower 83 which is mounted on an arm 34. This arm is secured to the leg 92 of arm 52 and its position with reference to it may be varied by means of an adjusting screw 85 which is screwed into a bar 86 attached to the leg 92 of the lever 62 and which is held in position by means of a lock nut 81.

The operation of the invention is as follows: When the motor [5 is energized, shaft 14 drives the shaft [3 through the springs 59 connecting the plates 5! and 53 together. Normally with the lever 62 in raised position as shown in Fig. 2, the shoe 65 is free from the brake drum 52 and the shaft I3 is driven at a constant uniform speed. If the control wire H is lowered to the position shown in Fig. 3, the collar i2 is moved away from lever 62 and spring 55 urges the said lever downwardly and the brake shoe 65 into engagement with drum 52. This places a drag upon the said drum which causes the relative movement between the driving element 53 and the driven element 5!. This causes the springs 59 to be tensioned until the force produced by the friction of the brake equals the force required to stretch the springs. The parts now rotate in relatively altered rotational relation. At the same time, the cam follower 83 is riding upon the cam 13. When. the said follower is raised sufficiently by the cam, the shoe 60 becomes disengaged from the drum 52 and the springs 59 bring the driven and driving elements back into normal relationship. As the shaft l4 rotates, cam 73 causes the driven element to be alternately retarded and accelerated and the tone generators to be alternately slowed down and speeded up. This produces the desired tremolo effect. By adjusting the tension on the spring 65 through screw 66, and by adjusting the screw 85, dilferent tremolo effects can be procured.

The advantages of the invention are manifest. The device is extremely simple in construction and positive in action. The tremolo eifect can be adjusted to produce an appreciable periodic variation in frequency or only a slight variation as desired. The device is entirely mechanical and can be readily installed in existing machines utilizing revoluble tone generator elements. j

Changes in the specific form of my invention, as herein described, may be made within the scope of what is claimed without departing from the spirit of my invention.

Having described my invention, what I claim as new and desire to protect by Letters Patent is:

1. In a tremoio a rotatable driving element and a rotatable driven element, a spring positively connected at one end to said driving element and positively connected at its other end to said driven element and constituting a flexible coupling continuously acting between said driving element and said driven element and affording limited relative rotational movement therebetween, a brake drum rotatable with said driven element, a brake shoe for cooperation therewith, guide means for guiding said brake shoe for movement toward and from said drum and restraining circumferential movement thereof relative to said drum, a rotatable cam driven by said driving element, a cam follower engageable with said cam and resilient means acting between said cam follower and brake shoe, and resilient means urging said brake shoe toward said drum, said cam operating in opposition to both of said resilient means.

2. In a tremolo a rotatable driving element and a rotatable driven element, a spring positively connected at one end of said driving element and positively connected at its other end to said driven element and constituting a flexible coupling continuously acting between said driving element and said driven element and affording limited relative rotational movement therebetween, a brake drum rotatable with said driven element, a brake shoe for cooperation therewith, guide means for guiding said brake shoe for movement toward and from said drum and restraining circumferential movement thereof relative to said drum, a rotatable cam driven by said driving element, an arm mounted on said guide means and movable relative to said guide means in a direction toward and from the axis of said brake drum, a cam follower carried by said arm and engageable with said cam, adjusting means for adjusting the position of said arm and brake shoe and resilient means for urging said brake shoe toward said drum, said cam operating in opposition to said resilient means.

CONRAD P. KRUEGER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 717,976 Dodge Jan. 6, 1903 841,342 Richards Jan. 15, 1907 1,180,695 Carlson Apr. 25, 1916 1,580,584 Church et al Apr. 13, 1926 2,009,383 Blume July 30, 1935 2,314,496 Hammond Mar. 23, 1943 2,435,933 Toolan Feb. 10, 1948 2,460,000 Flanagan Jan. 25, 1949 FOREIGN PATENTS Number Country Date 12,492 Great Britain May 12, 1912 

